I use this macro to quickly center my mouse cursor on my main screen. I have two large monitors and embarrassingly, I lose my mouse cursor occasionally.
This macro is also a good demonstration of some of the calculations with Keyboard Maestro variables.
The macro is triggered by the option-shift left click-release mouse action. It simply moves the mouse to the exact center of the primary monitor.
I take advantage of some of the built in KM tokens in this macro. For example the %Screen%Main% variable extracts the frame of the primary monitor.
Next, I use the Move Mouse action. Instead of hard coding in the location I want the cursor moved to, I use the array values that represent the frame of the screen. KM list values are accessed as if they were arrays (starting at 1). In this case, temp points to the value 2560. But since the Move Mouse action accepts a numerical value, I can actually use some basic math functions to generate the value. This is true of any action that uses a numerical value. They can all accept a calculations instead. Nifty.
UPDATE: I changed the trigger to be more compatible with applications that respond to cmd-click.